Electrical contact device



Sept. 18, 1951 sco-rr 2,568,465

ELECTRICAL CONTACT DEVICE Filed Jan. 5, 1949 Inventor:

H i s Att orh ey.

Patented Sept. 18, 1951 snsc'rarcar. CONTACT mavrcs Benjamin B. Scott,Schenectady, N. Y., assignor to General Electric Company, a corporationof New York Application January 3, 1949, Serial No. 68,818

3 Claims. (Cl. 201--63) My invention relates to electrical contactdevices more particularly to electrical contact devices for resistancewinding machines and has for its purpose the provision of a simple andreliable device to secure a continuous electrical contact to movingenamel insulated electrical resistance wire.

The manufacture of linear and non-linear precision resistances entailsthe placement of wire turns at exact positions on card brushing edgescorresponding to the formula to which the card is being wound. Placementaccuracy of turn positions is basically dependent upon the accuracy ofresistance measurement which is diiiicult of attainment at high windingspeeds in excess of 150 R. P. M. and for smaller than 0.0015" diameter.The present invention permits continuous contact of wire sizes as smallas 0.001" at ordinary speeds and winding speeds in excess of 300 R. P.M. where wire is of suflicient diameter to provide the required tensilestrength.

My invention eliminates these diiliculties by the use of an insulatedwheel having sharply ground peripheral serrations around which the wireloops as it is fed to the winding head. A roller of tough resilientnon-conducting material spring biased towards the toothed wheel causesthe teeth to penetrate the enamel insulation coating of the wire to makecontinuous contact with the metal.

Previously, a stripping device attached to the winding head removed aportion of the insulation to lay a section. of the wire circumferencebare along the whole length of the wire. This bare portion waspositioned outward on the finished resistance and contact with thebrushing edge of each turn was made by a flexible contact finger aftereach turn was wound; If the cumulative resistance to any turn did notconform to the cumulative resistance to the corresponding point on themaster resistance the succeeding turn was so positioned as to compensatefor the error.

In carrying out my invention, the sliding brush of the master resistancemeans is placed at the point on the master linear resistance having thesame cumulative master resistance as the cumulative resistance of thewire being wound from the start to the contacting device. As the windinghead and the cam device are moved by the same lead screw, the wire iswound on the card in a position corresponding to the position of equalresistance on the master resistance. Thus, my invention places each turnof wire in its true position rather than adjusting the position of eachturn of wire to compensate for the previous turn that has beeninaccurately positioned on the card.

For a more complete understanding of my invention, reference is directedto the accompanying drawing of one embodiment of my invention. Fig. l isa view of the contacting device mounted on the winding carriage of awinding machine and its position in relation to the resistance beingwound. Fig. 2 is a detailed perspective view of the contacting device.Fig. 3 is the wiring diagram of the machine.

Referring to the drawing, my preesnt invention may be embodied in acontacting device I which may be combined with a winding machine such asthat described in my copending application, S. N. 58,669 dated November6, 1948. Wire 2 from a reel, not shown, threads over guide pulley 8pivoted upon the non-conducting base 4 which is mounted upon the windingcarriage 5 of the winding machine 6. The wire is looped once around theperipherally serrated wheel 1 of electrically conducting material andhaving sharp teeth I pivotally mounted upon the member 8 which ismounted upon the base 4 upon a pivot at 9 and oscillates between stopsl0 and II. Components corresponding to serrated wheel I, member 8, base4, pivot 9, and stops l0 and II comprise an apparatus which forms aportion of the subject matter of my copending application, Serial No.82,113 filed March 18, 1949, on a "Contact Device for Moving Wires. Awheel I4 having a tough tire l5 of Vinylite, or other appropriateresilient material, is pivotally mounted on the arm I! pivoted upon themember 8 at l3. A spring H with adjustment I8 is connected between arml2 and member 8 biasing the wheel l4 towards the serrated wheel I withsufiicient force to cause the serrations to pierce the varnish or enamelinsulating coating of the wire 2 'to make continuous contact with themetal {of the wire.

The motor l9 operates the .drive shaft through the worm 2| and wormwheel 22. The shaft 20 operates the divided winding shaft 23 through thegears 24, 25 and 26, 21 to wind the wire on the card 28. Gears 29, 29',differential 30, gears 3i and 32 operate the lead screw 33 whichprovides simultaneous motion to the lead carriage 5 and the cam carriage34. The cam 35 and the follower 36 cause the contact 31 to move over themaster resistance 38 to vary the master resistance between the wires 39and 40.

The beginning 4| of the resistance being wound is electrically connectedthrough the commutator 42 insulated from the shaft 23 and the springcontact 43 to the wire 44. A terminal 45 attached to the member 8 isprovided with a spring ontact bearing upon the serrated wheel I toconnect the serrated wheel to the wire 49, thus allowing a continuousreading of the resistance being wound between wires 44 and 46.

The subtended portion of the master resistance and the resistance beingwound, are series connected in a Wheatstone bridge circuit with theratio resistors 48 and 49. A D. C. supply is connected from a pointbetween the ratio resistors to a pivot between the master resistance andthe resistance being wound. A galvanometer 50 connected across the ratioresistors indicates direction of unbalance of the bridge circuit.

A hand wheel 50 operating through the worm 52, the worm wheel 53 and theshaft 54 projecting through the hollow gear 3| operates the spider ofthe differential 30 to change the position of the lead screw 33 withrelation to the winding shaft 23 increasing or decreasing the lead ofwinding upon the card 28. At the same time the slider 31 is moved on themaster restistance 38 so that when the galvanometer reaches zero, thewire is wound on the card at the point corresponding to the point ofcontact of brush 3'! on the master resistance.

By the use of the method outlined in my invention, continuous positivecontact is maintained regardless of the speed of travel of the movingwire. The wire insulation is so slightly damaged by the entry of thesharp edges of the contacting wheel that the nicks caused by the teethon a small wire having a thin insulation coating can be seen only undera microscope. Preferably as shown the serrated wheel is on the same sideof the wire as the card so that the wire is wound on the card with thenicks facing or against the card. The side of the wire provided with thenicks is, therefore, always on the compression side of the wire surfacewhereby fracture of the wire is prevented, as would be possible if thewire were wound with the nicked sides on the outside of the finishedcard where the wire surface is in tension.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A contacting device for making continuous electrical contact with amoving wire coated with an insulation comprising a rotatable serratedconducting wheel of electrically conducting material for penetratingsaid insulation and maintaining electric contact with a loop of saidwire,

a smooth wheel provided with a resilient tire, a

spring biasing said smooth wheel toward tangential contact with saidserrated conducting wheel so as to press the wire against the teeth oisaid serrated wheel to cause the teeth to penetrate the insulation onthe wire and make a continuous electrical contact between the metal ofthe moving wire and said serrated wheel 2. In a winding machine forwinding turns of resistance wire coated with insulation upon a turnsupporting card, a contacting device for making continuous electricalcontact with said wire during winding comprising a serrated conductingwheel for penetrating said insulation and maintaining electric contactwith a loop of said wire, a smooth circumferenced wheel in rollingcontact with said wire loop, an adjustable spring biasing said smoothwheel towards said serrated conducting wheel so that the serrations ofsaid serrated wheel pierce said insulation to contact the metal of saidwire, a terminal provided with a spring contact engaging said serratedwheel so that continuous electrical contact is maintained between saidwire and said terminal.

3. An electrical contacting device for making continuous electricalcontact with a moving wire coated with an insulation, comprising twocoacting wheels, one of said wheels being provided with a resilient,circumferential surface, the other of said wheels provided withcircumferential serrations, means for passing a wire between saidwheels, a spring for biasing one of said wheels toward the other so thatsaid serrations pierce the insulation on the wire and provide acontinuous electrical contact between the metal of the moving wire andsaid serrated wheel.

BENJAMIN B SCOTT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,992,859 Cooper Feb. 26, 19352,069,623 Pickhaver Feb. 2, 1937 FOREIGN PATENTS Number Country Date661,959 Germany Sept. 17, 1932

